Your C is not standard C

The article discusses significant incompatibilities between the C programming language as defined by its official standard and how it's actually implemented in widely-used compilers like GCC and Clang. Key examples include GCC and Clang treating "asm" as a reserved keyword by default despite it being a valid identifier in standard C, GCC's incorrect implementation of the FLT_ROUNDS macro which should dynamically reflect runtime floating-point rounding modes, and the lack of support for standard pragmas that control floating-point behavior—with GCC ignoring all five standard pragmas even 27 years after their introduction in C99.